Detection apparatus



Oct. 6, 1964 J. L. HODGDON DETECTION APPARATUS Filed Feb. 5, 1962 2; Sheets-Sheet 1 INVENTOR.

[4245: Z. HODG'DU/V Oct. 6, 1964 J. L. HODGDON DETECTION APPARATUS 2 Sheets-Sheet 2 Filed Feb. 5, 1962 1+ ans/V United States Patent 3,151,819 DETECTHON APPARATUS James L. Hodgdon, Plainfield, N.J., assignor to Radio Corporation of America, a corporation of Delaware Filed Feb. 5, 1962, Ser. No. 170,869 6 Claims. (til. 242--54) This invention relates to apparatus for detecting breaks in fine wires.

In a known machine for making grids, a grid frame is provided, and a plurality of lateral wires in a parallel array in the plane of the frame are fed towards it. The wires are fed under tension so that a plurality thereof, properly tensioned, overlie the frame when the feeding operation ceases. The wires under tension that overlie the frame are then welded to it, the wires not being fed during the welding operation. After the welding operation, the wires are cut off beyond the frame. After forming the welded grid lateral wires to their final shape, the grid is completed and the completed grid is removed, ending the cycle.

In this grid making machine, if a wire breaks, feeding of the broken wire ceases. A grid may therefore be produced from which one lateral wire is missing, result ing in the making of an imperfect grid. Imperfect grids will continue to be produced until the operator of the machine notices that a lateral wire is missing from a completed grid. The operator thereupon stops the machine and threads the broken wire or wires from the supply spool or spools into the grid making machine. A device for detecting that a wire is broken or a device for stopping the grid making machine upon detection of a broken Wire would prevent the continued making of imperfect grids.

The grid lateral wire used in making grids is very fine, and in the grid making machine mentioned above a great many lateral wires are supplied simultaneously. A wire break indicator which includes a feeler that contacts a wire adds to the tension on the wire. These feelers may cause uneven tension at various times in the same wire or different tensions as between the several grid lateral wires fed to the grid making machine. A feeler may even cause breaking of one of the wires. Also, a feeler, feeling a very fine wire may have a groove cut therein by the wire, resulting in a higher friction between the feeler and the wire after a groove is worn into the feeler than when a new unworn feeler is used resulting in nonuniform tension as between several lateral wires.

An important further reason for avoiding the use of a feeler is that a feeler flattens fine wire slightly but sufficiently so that the wire tends to curl or spiral, rendering defective grids made from such flattened wires. Furthermore, each time a spool of wire is replaced, or when stringing a broken wire from a spool to the grid making machine, the feeler is put in contact with the wire, requiring an additional operation and care and skill on the part of the operator.

It is an object of this invention to provide an improved apparatus for detecting a break in a wire which is to be fed intermittently.

It is another object of this invention to provide an improved apparatus for detecting a ruptured wire and which apparatus dispenses with the use of a contacting wire feeler.

It is a further object to provide an improved apparatus for properly tensioning a wire and for detecting a break in a Wire which is to be fed intermittently.

Apparatus in accordance With this invention comprises a plurality of break detectors, each of which includes a spindle on which a spool holding the grid lateral wire may be mounted, whereby, upon rotation of the spool "ice while feeding lateral wires therefrom, the spindle is rotated. A clutch plate is mounted on the spindle and is provided with a switch. The switch is position responsive, that is, upon rotation of the clutch plate through a small angle, the switch changes to its other state or condition, eg from closed to open (or it may be from open to closed). Means are provided for causing the clutch plate to be frictionally engaged with a portion of the spindle, to cause the clutch plate to rotate enough to change the state or condition of the switch in response to rotation of the spindle caused by feeding Wires from the spool. A second, normally open switch may be provided, connected in a series circuit with the position responsive switch, a source and a transducer, to indicate, upon closing said second switch, the position of the position responsive switch. If the wire is broken, the clutch plate will not be rotated and the condition of the position responsive switch will not be changed. responsive switch is closed, both switches in the series will be closed energizing the transducer. The transducer may provide a signal, or it may cause energization of a relay to stop the grid making machine, as by disconnecting the power source therefrom.

This invention is more fully explained hereinafter taken together with the several figures of the drawing in which:

FIG. 1 is a plan view of three of the plurality of wire break detectors of this invention, feeding grid lateral wires to a grid making machine;

FIG. 2 is a cross sectional view of FIG. 1 on line 22 thereof;

FIG. 3 is a cross sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is a diagrammatic showing of the circuit connections of the break detector of this invention;

FIG. 5 is a diagram showing the relative timing of the opening and closing of the switches comprising parts of the circuit of FIG. 4.

As shown in FIG. 1, a wire 10 is fed from each of a plurality of spools, each associated with a wire break detector 12, to a grid making machine 14. Only a few wires 10 are shown in FIG. 1. However, it will be understood that as many wires 10 are fed as is required by the design of the grid being made. While only three break detectors 12 are shown in FIG. 1, a break detector is provided for each wire fed to the grid making machine 14. The wires 10 run over a comb 16 and through the grooves 18 thereof and under a device 20 for intermittently feeding the wires comprising a portion of the grid making portion of the grid making machine 14. Since the structure of the grid making machine is known and since it forms no part of this invention, the grid making machine is not further described.

The break detectors 12 each includes a tension adjusting device, as will be explained, whereby the wire is supplied to the grid making machine under the proper tension.

Referring to FIGS. 1 and 2, a support rack 22 is provided to which the break detectors 12 are fixed. Each detector includes a supporting rod 24 extending through the rack 22. It is suflicient to describe in detail the detector shown in FIG. 2, the others being similar. A disk 26 of magnetic material, such as iron, is threaded on the rod 24 to the right of rack 22, as viewed in FIG. 2. A nut 28 on the end of the rod 24 to the left of rack 22 locks the rod 24 and disk 26 on the rack 22. A felt disk 30 is provided on the rod 24 to the right of disk 26 If the condition mounted on rod 24 beyond the right-hand end of spindle 32. Jam nuts 40 are provided, threaded onto rod 24 to the right of spring 38 to provide an adjustable amount of friction between the. spindle 32 and the felt disk 30 whereby the tension on the lateral wire 10 may be adjusted.

The break indicator comprises an annular clutch coil holder 42 which is fixed to support rack 22 by means of screws 44. The coil holder 42 is concentric with rod 24 and surrounds the periphery of iron disk 26, felt disk 30 and the disk portion 36 of spindle 32. An annular groove is provided in the periphery of, and near the righthand edge of, coil holder 42 to hold a clutch coil 46. The break indicator includes further a clutch plate 48 rotatably mounted on the cylindrical portion 34 of spindle 32, near the right-hand face of the disk portion 36. This clutch plate 48, as shown in elevation view in FIG. 3, has the shape of the included figure of a large upper circle and a smaller lower circle connected by tangent lines. The plate 48 mounting is coaxial with the axis or center of the larger circle. A mercury switch t] is mounted on a face of the lower end of the clutch plate 48 by bracket 52, and preferably on the face of the plate 48 towards the coil holder 42. Aplurality of retaining rings 53, 54 and 55 are fixedly mounted on the cylindrical portion 34 of spindle 32, one thereof, 53, being between clutch plate 48 and the adjacent face of disk portion 36 of spindle 32, and two thereof, 54 and 55, being on spindle 32 to the right of plate 48. The two retaining rings 53 and 54 adjacent the two sides of the clutch plate 48, act to retain clutch plate 48 in position on spindle 32 but permit free rotation of clutch plate 48. Ring 53 may comprise a portion of spindle 32. A spool 56 on which lateral Wire is stored is pushed onto spindle 32 and in frictional engagement therewith, until it bears against the third or right-hand retaining ring 55.

The wiring diagram for the break detectors is shown in FIG. 4. All the clutch coils 46 are connected in parallel with each other and in series with a microswitch 57 and a power supply 58, preferably of direct current to avoid jitter of clutch plate 48. All the mercury switches 50, which are closed in the position thereof shown in FIG. 3, are connected in parallel with each other and in series with power source 60, microswitch 62 and the coil of normally closed relay 64, this relay here acting as a transducer. The contacts of normally closed relay 64 are connected in series with supply 66 and the main drive, not shown, of the grid making machine, whereby, as will be explained, the grid making machine 14 is stopped upon the detection of a break and stays stopped until restarted by the operator. Or, if desired, a signal, such as a bell or light with a latching means to keep it on until noticed (since the signal would go off each time the break de tector is reset, as will be explained) may be substituted for the relay 64. In this latter case, the operator will turnoff the machine upon noticing the signal. Cams 68 and 70, mounted on shaft 72 for rotation therewith, and driven from the main drive, not shown, of the grid making machine 14, close normally open switches 57 and 62 respectively, in accordance with the timing chart of FIG. 5. In this chart the cycle of operation is considered to be 360, one grid being made each time shaft 72 rotates through 360. The switch 57 is closed by cam 68 between and 130 and is open at all other times. The switch 62 is closed by cam 70 between 80 and 120 and is open at all other times.

Operation of the break detector is as follows: Spools 56 containing lateral wire 10 are each pushed onto and into frictional engagement with a respective spindle 32 until the spool contacts the retainer ring 55. At this position thereof, spool 56 .fits tightly enough on spindle 32 to turn with it. The wire 10, from each spool is strung through a guide groove 18,0f comb 16 and through intermittent wire feeding meansof the grid making machine 14. The predetermined desired tension on wires 10 is provided by adjusting the pressure between disk portion 36 and felt washer by rotating jam nuts and thereby adjusting the pressure on compression spring 33.

At the beginning of the cycle, no wire is being fed and the clutch plates 48 are all vertical, that is, they are in the position shown in FIGS. 2 and 3. In this position of the clutch plate 48, the switches 50, which may be mercury switches carried by the clutch plate, are closed. Also as shown in FIG. 5, switches 57 and 62 are open at the beginning of the grid making cycle. Therefore, no current is applied to clutch coil 46 or to relay 64 at the beginning of the cycle.

At the beginning of the grid making cycle, the grid making machine 14 starts to pull all the wires 10. Feeding of the wire from spools 56 cause all the spools to rotate clockwise, as viewed in FIG. 3, rotating spindles 32 with them against the friction between felt disks 30 and disk portions 36. However, since each clutch plate 48 is mounted for free rotation on its spindle 32, the clutch plates 48 remain in their vertical positions, as shown in FIG. 3, and therefore switch remains closed. Since switch 62 in series with all switches 50 is open during the early part of the grid making cycle, relay 64 is not operated at this time.

At 10 of the cycle, while grid wire is still being fed to the grid making machine 14, cam 68 closes switch 57 and direct current is applied to all the coils 46 in parallel, each coil produces a magnetic field linked with clutch plate 48 thereby attracting clutch plate 48 towards it, that is, to the left as viewed in FIG. 2, increasing the friction between the clutch plate 48 and retaining ring 53. As the wires 10 are still being pulled, each spindle 32 is rotated and the friction between each clutch plate 43 and its retaining ring 53 is sufiicient to cause clutch plate 48 to rotate through an angle to such a position that the switch 50 mounted thereon is opened. This friction between the clutch plate 43 and retaining ring 53 is not sufiicien't, however, to cause rotation of clutch plate 48 much further than the few degrees necessary to open switch 50. The switch 57 remains closed for the next 120 during which wires are fed to the grid making machine. Therefore, if no wire 10 isbroken, the switches 50 of the break detectors 12 will all be opened during the period from shortly after 10 to 130 of the cycle of operation of grid making machine 14. However, if a wire 10 is broken, a spool 56 will not be turned and its clutch plate 48 will remain in its vertical position and its switch 50 will remain closed thereby operating the relay 64 during the time switch 62 is closed, as will be explained.

All wire necessary for the making of one grid is pulled during the first 130 of the cycle of operation. At 130, the cam 68 permits the switch 57 to open, ending the magnetic attraction between the clutch plate 48 and clutch coil 46, thereby ending the friction between the clutch plate 48 and retainer ring 53. Plate 48 resumes its vertical position at which position the switch 50 is closed, if it has been previously rotated out of vertical position. This opening of switch 57 at 130 results in a resetting of the break detector, as will be more fully explained below.

The switches 50 which are all connected in parallel, are connected in series with switch 62, relay 64 and power source 69. Therefore, unless switch 62 is closed, and one of the switches 50 is also closed, relay 64 will not be operated. Cam 7 0 closes switch 62 at of the cycle of the operation of the break detector 12, allowing switch 62 to remain closed until of the cycle of the break detector. If a wire 10 is broken, the corresponding switch 50 will remain closed as noted above, and upon closing of the switch 62 in series therewith, the relay 64 will be operated to disconnect the source of electrical supply 66 from the main drive (not shown) of the grid making machine 14, whereby defective grids are not made thereby. Since, as noted above, enough lateral wire is fed during about the first of the cycle, the grid making machine does not pull wire from about 130 to the end of its cycle. During this latter part of the cycle, the grid making machine 14 welds or otherwise fixes the lateral wires to the grid frame (not shown). The grid machine begins to pull wire again at about 0 of its cycle, and the cycle is repeated.

As noted, the switches 50 are all closed at the beginning of each cycle. The switch 62 is provided in series with the switches 50, so that the grid making machine 14 can start. The switch 62 should be open long enough to permit machine 14 to pull wire far enough to open switches 50, and the machine 14 will then continue if no wire is broken.

The break detector 12 should be reset after each grid has been made. This is so because the clutch plate 48 will retain its last angular position as long as clutch coil 46 is energized. That is, as long as coil 46 is energized, the friction between clutch plate 48 and retaining ring 53 will hold clutch plate 48 in the angular position where the turning of the retaining ring 53 with the spindle 32 has rotated the clutch plate 48. Therefore, if the break detector is not reset, when a further grid is being made by grid making machine 14, the clutch plate will be in the position that indicates an unbroken wire 10 even though the wire 10 is in fact broken. The resetting operation is accomplished by cam 68 and microswitch 57, breaking the circuit to the coils 46, ending the attraction of clutch plate 48 to spindle portion 36 and permitting the clutch plate 48 to resume its original, vertical position.

It will be noted that clutch plate 48 must be rotated through a certain minimum number of degrees before switch 50 mounted thereon is opened. When making narrow grids requiring a very small length of lateral wire 10, the rotation imparted to clutch plate 48 by the small amount of lateral wire 10 pulled off a spool 56 for making one such grid, may not be suflicient to cause opening of switch 50 whereby the break detector 12 will indicate the wire is broken when in fact it is not broken. To detect breaks when making such narrow grids, the rotation of plate 48 may be cumulative, that is, the break detector will be reset only once for two or more cycles of the grid making machine. Then, the turning of the plate 48 produced by the production of two or more grids is added up and the cumulative turning brings plate 48 to the position where the switch thereon will be opened, if the lateral wire is unbroken. Also, the switch 62 in series with the switch 50 will be closed once for a corre sponding number of cycles of the grid making machine and will be opened just before the break detector is reset. Both switches 57 and 62 will be held open during the period of time after the break detector is reset that it takes to fix a set of lateral wires to a frame of a grid. To provide this operation of switches 57 and 62, shaft 72 of FIG. 4 may be driven at a submultiple rotational speed when making such narrow grids, as compared to its speed when making wider grids. For example, considering 720 as the length of the cycle necessary to make two such narrow grids successively, shaft 72 may be driven, by the main drive of the grid making machine, at such speed and cams 68 and 70 may be so formed that cam 68 keeps switch 57 closed from 10 to 490, and cam 70 keeps switch 62 closed from 440 to 480, both switches being open from 490 to 720 (plus the first 10 of the next pair of cycles). During the period 130 to 360, the first set of lateral wires are fixed to the first grid frame. During the period of 490 to 720, the second set of lateral wires are fixed to the second grid frame. In this manner, the break detector of this invention will detect a break in a lateral wire while narrow grids are being made, after sufiicient lateral wires for two are fed to the grid making machine. For a still narrower grid, the shaft will be rotated, still slower and the cam 68 will close switch 57 just after wire is fed to the first grid and will hold it closed until after sufficient wire is fed for three grids, for example, cam 70 will close switch 62 after clutch plates 48 have been rotated (the wires being intact) to the point where switches 50 are open and cam 70 will allow switch 62 to open just before switch 57 opens. When such narrow grids are being made, the device of this invention will detect a broken wire while making a plurality of successively made grids, and not for each individual grid.

What is claimed is:

1. Apparatus for detecting a break in any one of a plurality of wires comprising a plurality of spindles, each spindle including a frictional portion, each spindle having a clutch plate of magnetic material mounted for rotation thereon, a different position responsive switch mounted on each clutch plate, a different coil adjacent each clutch plate for producing a magnetic field linked with a respective clutch plate, means for intermittently pulling said wires, means to rotate said spindles in response to the pulling of the respective unbroken wires, said coils upon energization thereof causing said clutch plate to be frictionally engaged with said frictional portion of said spindle to rotate therewith, a plurality of said coils being connected in parallel with each other and in series with a power source and a further switch, a plurality of said position responsive switches being connected in parallel with each other and in series with a still further switch and a power source and a transducer, means to close said further switch during the pulling of said wires, and means to close said still further switch during a later portion of the period of closure of said further switch.

2. Apparatus for tensioning a wire and for detecting a break therein, comprising a support, a rod extending through said support and holding a disk thereagainst, a friction disk mounted on said rod in contact with said first mentioned disk, a spindle rotatably mounted on said rod and having an end in contact with said friction disk, a spring mounted on said rod, one end of said spring contacting the other end of said spindle, a pair of jam nuts threadedly mounted on said rod and holding said spring in contact with the other end of said spindle, said spindle being adapted to receive a spool of wire mounted thereon, a clutch plate of magnetic material rotatably mounted on said spindle, a position responsive switch mounted on said clutch plate, an annular coil for producing a magnetic field mounted on said support and surrounding said rod, said clutch plate being adjacent said coil, said spindle including a friction element between said clutch plate and said coil, said clutch plate being frictionally engaged with said friction element upon energization of said coil, whereby upon rotation of said spindle by pulling said wire off said spool during the energization of said coil, said clutch plate is frictionally rotated.

3. Apparatus for tensioning a plurality of wires and detecting a break in one thereof, comprising a plurality of spindles, each having a frictional portion, each spindle having a clutch plate of magnetic material mounted for rotation thereon, a position responsive switch mounted on each clutch plate, frictional means for resisting rotation of said spindles with respect to a support, a coil for producing a magnetic field in the vicinity of each of said clutch plates and linked with said clutch plate, means for intermittently pulling said wires, means to rotate said spindles responsive to the pulling of unbroken respective ones of said wires, said coils upon energization thereof causing said clutch plates to be frictionally engaged to said frictional portions of said spindles to rotate therewith, a plurality of said coils being connected in parallel with each other and in series with a power source and a further switch, a plurality of said position responsive switches being connected in parallel with each other and in series with a still further switch, a power source and a transducer, means to close said further switch during the pulling of said wires, and means to close the still further switch during a later portion of the closure of said further switch.

'3' 4. Apparatus for detecting a break in a wire comprising:

a support,

a spindle rotatably mounted on said support for carrying the wire,

means responsive to pulling said wire while said Wire is unbroken to rotate said spindle,

a clutch plate of magnetic material rotatably mounted on said spindle,

a coil mounted in the vicinity of said clutch plate for producing a magnetic field for attracting said clutch plate toward said coil,

means connected to said coil for energizing said coil during rotation of said spindle,

a friction element mounted on said spindle between said coil and said clutch plate,

said clutch plate being pulled into frictional contact with said friction element when said coil is energized for causing said clutch plate to be rotated by said spindle from a first to a second position, said clutch plate being maintained in said second position by said friction element while said coil is energized, and

sensing means connected to said clutch plate and being operative to detect the presence of said clutch plate in said first position while said coil is energized and while said wire is being pulled.

5. Apparatus for tensioning a wire and detecting a break therein comprising:

a support,

a spindle rotatably mounted on said support for carrying the wire,

means responsive to pulling said wire while said Wire is unbroken to rotate said spindle,

frictional means disposed between said spindle and said support for resisting rotation of said spindle,

a clutch plate of magnetic material rotatably mounted on said spindle,

a coil mounted in the vicinity of said clutch plate for producing a magnetic field for attracting said clutch plate toward said coil,

means connected to said coil for energizing said coil during rotation of said spindle,

a friction element mounted on said spindle between said coil and said clutch plate,

said clutch plate being pulled into frictional contact with said friction element when said coil is energized for causing said clutch plate to be rotated by said spindle from a first to a second position, said clutch plate being maintained in said second position by said friction element While said coil is energized,

a position responsive switch mounted on said clutch plate and actuated when said clutch plate is moved from said first to said second position, and

sensing means connected to said switch, said sensing means being operative to detect the presence of said clutch plate in said first position while said coil is energized and while said wire is being pulled.

6. Apparatus for tensioning a wire and detecting a break therein comprising:

a support,

a spindle rotatably mounted on said support for carrying the wire,

means responsive to pulling said wire While said wire is unbroken to rotate said spindle,

frictional means disposed between said spindle and said support for resisting rotation of said spindle,

a clutch plate of magnetic material rotatably mounted on said spindle,

a coil mounted in the vicinity of said clutch plate for producing a magnetic field for attracting said clutch plate toward said coil,

means connected to said coil for energizing said coil during rotation of said spindle,

a friction element mounted on said spindle between said coil and said clutch plate,

said clutch plate being pulled into frictional contact with said friction element When said coil is energized for causing said clutch plate to be rotated by said spindle from a first to a second position, said clutch plate being maintained in said second position by said friction element while said coil is energized, and

sensing means connected to said clutch plate and being operative to detect the presence of said clutch plate in said first position while said coil is energized and While said wire is being pulled.

References Cited in the file of this patent UNlTED STATES PATENTS 

1. APPARATUS FOR DETECTING A BREAK IN ANY ONE OF A PLURALITY OF WIRES COMPRISING A PLURALITY OF SPINDLES, EACH SPINDLE INCLUDING A FRICTIONAL PORTION, EACH SPINDLE HAVING A CLUTCH PLATE OF MAGNETIC MATERIAL MOUNTED FOR ROTATION THEREON, A DIFFERENT POSITION RESPONSIVE SWITCH MOUNTED ON EACH CLUTCH PLATE, A DIFFERENT COIL ADJACENT EACH CLUTCH PLATE FOR PRODUCING A MAGNETIC FIELD LINKED WITH A RESPECTIVE CLUTCH PLATE, MEANS FOR INTERMITTENTLY PULLING SAID WIRES, MEANS TO ROTATE SAID SPINDLES IN RESPONSE TO THE PULLING OF THE RESPECTIVE UNBROKEN WIRES, SAID COILS UPON ENERGIZATION THEREOF CASING SAID CLUTCH PLATE TO BE FRIC- 